playback in FXstack preview issue

[Peter Wassink]

This is some feedback from a user new to tvpaint.
it was something that confused them.

When you playback an animation in a clip using the playback preview button (on the remote control or in the project window)
if you click once it plays and if you click again it pauzes on the current frame. as you would expect.

but if you have the fxstack preview on
if you click once it starts and if you click again, to pauze, it doesn't stop but it "goes to last frame".

So it seems a bug... at least its not consistent behaviour and not something you would expect to see happening
it becomes very apparent if you are controlling the start/stop action with the spacebar.
doing that in preview mode feels like you lost control